This group of studies will determine if breathing is coordinated with locomotor activities in healthy young infants during the first year of life. Direct comparisons will be made with adults. Activities will be determined which are especially likely to show coordination. These studies will determine if perturbations to one rhythmic activity will also cause perturbation of the second activity, if the coordination is dependent on maturation, the time course of this development will also be investigated. Finally, it will be determined if the coordination is normal in infants born prematurely, and how this coordination develops in this group of infants. It is important to know how active movements affect breathing in young infants. It is particularly significant to understand this relationship for infants who are at risk for respiratory problems. These studies will provide the ground work necessary for future extension of the work to infants at risk.